An uninterruptible power supply (UPS) gradually becomes a trend in a power supply solution in a data center because of relatively high whole-process power supply efficiency and relatively high power supply reliability. An increasingly high requirement is imposed on reliability of the data center, and a requirement on a data center already reaches a tier 4 (an annual mean down time does not exceed 24 min). Therefore, a new requirement is imposed on reliability of power supply to the data center, which not only requires low efficiency of each power supply part, but also requires a longer backup time of a battery.
Currently, a power supply method in the data center is performing backup at a power-supply input end to implement higher reliability. However, a battery pack used for backup can supply backup power to a load of only one voltage level. In this case, low utilization of the battery pack is caused.